The International Telecommunication Union (ITU) raises relatively stringent requirements on a next-generation mobile communication system, namely an International Mobile Telecommunications-Advanced (IMT-A). The requirements may include, for example, a maximum system transmission bandwidth reaching e.g., 100 MHZ, a peak rate of uplink and downlink data transmission reaching e.g., 1000 Megabits per second (i.e., 1 Gbps) and 500 Megabits per second (i.e., 500 Mbps), and a very high requirement on average spectral efficiency of the system, especially on edge frequency spectrum efficiency. In order to be better compatible with existing standards of Long Term Evolution (LTE), reduce the complexity of standardized work and support flexible application scenarios, the 3rd Generation Partnership Project (3GPP) proposes a Carrier Aggregation (CA) technology, which may achieve a larger bandwidth by aggregating multiple component carriers.
The carrier aggregation function may meet a higher requirement on bandwidth for a next-generation mobile cellular communication system, namely, a Long Term Evolution Advanced (LTE-A) system, and may serve as a necessary technology for guaranteeing backward compatibility with the LTE system. At present, the maximum bandwidth supported by an LTE system is e.g., 20 MHz, while the LTE-A system may achieve a maximum transmission bandwidth of up to e.g., 100 MHz through a carrier aggregation function.
The carrier aggregation may refer to aggregation of two or even more carriers (e.g., up to five carriers) by a base station (e.g., an Evolved Node B, which may be abbreviated as eNB). The aggregated carriers may be sent to user equipment (UE) by the base station via e.g., a Radio Resource Control (RRC) reconfiguration message, so that the UE may perform service transmission by virtue of the aggregated carriers. Among the aggregated carriers, a carrier, which keeps RRC connection with the UE, may be referred to as a Primary Carrier Component (PCC) and a cell corresponding to the PCC may be called as a Primary Cell (Pcell); and a carrier other than the PCC may be referred to as a Secondary Carrier Component (SCC) and a cell corresponding to the SCC may be called as a Secondary Cell (Scell). The carrier aggregation may include three scenarios as follows: contiguous intra-band carrier aggregation, non-contiguous intra-band carrier aggregation and inter-band carrier aggregation.
In a continuous evolution process of 3GPP, more and more spectrum resources may be gradually applied to an LTE system, so that frequency overlapping phenomenon may exist in different frequency band ranges of LTE, that is, the same physical frequency may correspond to multiple frequency band indicators. Due to the fact that the carrier aggregation capability of the UE may be closely related to the frequency band, even for an overlapped frequency band, if the UE does not support carrier aggregation for this frequency band, the carrier aggregation operation cannot be carried out. Therefore, even though carrier aggregation can be carried out for an actual physical frequency point, due to the limitation of the cell frequency band or the adjacent cell configuration of the base station side, or due to the restriction of carrier aggregation capability of the UE, service throughput of the UE may not be improved and system performance may not be improved, which may seriously influence the user experience.